What's difference between ref and type in XML schema

I am bit confused regarding referring an element  and creating a data
type for an element and referring it.
E.g.
Referring by type
<xsd:element name="A" type="AType" maxOccurs="unbounded"/>
<xsd:complexType name="AType">
	..
</xsd:complexType>

Referring by element itself
<xsd:element ref="A" maxOccurs="unbounded"/>
<xsd:element name="A">
	<xsd:complexType>
	...
	</xsd:complexType>
</xsd:element>



regards,
-Ranjan